1. Field of the Invention
The present invention relates to a burner for generating soot, and a furnace to deposit soot on the surface of metal strip such as stainless steel strip using the same burner for generating soot.
2. Description of the Related Art
In a manufacturing process of cold rolled stainless steel strip, a continuous annealing furnace is incorporated, and the stainless steel strip after cold rolling is heated and annealed mainly by, for example, radiation heat. In such continuous annealing furnace, the stainless steel strip reflects the heat rays owing to its excellent surface gloss, and the absorption efficiency of radiation heat is low, and it takes time to raise temperature, and the heat treatment capability of the annealing furnace is poor.
Accordingly, to enhance the heat treatment capability of stainless steel strip, it is attempted, for example in the Japanese Examined Patent Publication (KOKOKU) No. JP-B2 60-56213 (1985), to deposit soot on the surface of the stainless steel strip to be annealed by using soot generating burner, and heat quickly by raising the heat absorption rate of the stainless steel strip.
A conventional soot generating burner is disclosed, for example, in the Japanese Unexamined Patent Publication (KOKAI) No. JP-A 2-97812 (1990). In this prior art, soot is generated by burning the fuel gas at an air ratio of 0.3 or less. When soot is generated at such low air ratio, soot also deposits on the tip of the burner, and the soot deposit may clog the nozzle opening, or the soot deposits gradually to build up into a lump, and the soft lump of soot is casbonized by flame and solidified into a coke form, so that a stable flame may not be formed. For example, when forming a downward flame by a conventional soot generating burner, since the specific gravity of the flame is small, the flame contacts with the burner tiles and is cooled, and the generated soot often builds up on the nozzle opening, and the soot grows up like an icicle, and the soft lump of soot is carbonized and solidified as mentioned above, and deposits near the nozzle opening. Furthermore, the soot gradually building up at the nozzle tip drops onto the steel strip and is burnt imperfectly in the annealing furnace, and may be stagnant in the subsequent cooling zone or pickling bath, thereby contaminating the apparatus. Or, if the soot generating burner is installed to form an upward flame, the soot builds upward to the periphery of the nozzle tip, and same problems are caused.